Self-adjusting stay-bolt.



M. F. COX.

SELF ADJUSTING STAY BOLT.

APPLICATION mum Patented Sept. 2, 1913.

2 SHBETB-SHEET 1.

WITNESSES ,%W%w @MVV.

M. F. COX.

SELF ADJUSTING STAY BOLT.

APPLICATION IILED OUT. 30, 1912.

' 1,072,315, Patented Sept. 2, 1913.

2 SHEETS-SHEET 2.

Ti e WITNESSES INVE TOR MILLARD F. COX, 0F LOUISVILLE, KENTUCKY.

SELF-ADJUSTING STAY-BOLT.

Specification of Letters Patent.

Patented Sept. 2, 1913.

Application filed October 30, 1912. Serial No. 728,706.

To all whom it may concern:

Be it known that I, MILLARD F. Cox, a citizen of the United States, residing at Louisville, in the county of Jefferson and State of Kentucky, have invented certain new and useful Improvements in Self-Adjusting Stay-Bolts, of which the following is a specification.

This invention relates to an improvement in stay bolts and particularly to selfadjusting stay bolts for staying two walls between which relative movement or vibration is liable to occur when in use, as for instance the walls of steam boilers, the improved device being intended to displace the rigid stay bolt wherever used, as for instance when staying the roof, sides and back and front sheets of fire boxes or similar structures.

The object of the invention is to properly brace the walls and avoid the breaking incident to rigid stay bolts, as well as to compensate for error in design and irregularities of construction, with particular reference to the movements of boiler sheets under expansion and contraction, the effects of which in all types of locomotive boilers are so difficult to definitely trace.

The invention will be fully understood upon reference to the illustrative embodiments thereof disclosed in the accompanying drawing, in which Figures 1, 2, 3 and 4 are axial sections showing fragmentary portions of two boiler sheets stayed, in each instance, by the selfadjusting stay bolt forming the subject matter of the present invention; each view showing the same bolt head seat and cap associated with a different size of bolt; Figs. 5 and 5 show, by top plan view and axial section, a form of cap suitable for use in carrying out the present invention, and Figs. 6 and 6 show, by side elevation and axial section, the bolt head and the threaded sleeve forming the seat therefor.

1, 2, represent the outer boiler sheet and the fire box wall of a locomotive steam boiler.

3 is the stay belt which is threaded and riveted at 4 in the inner wall 2 and is connected to the outer wall by a seat 5 which permits the bolt to adjust itself angularly in response to relative movement in the planes of the sheets, and also to permit Vibration of the bolt without imposing strains upon it; this seat being provided with a cap 6 which renders it steam tight.

The novel construction of the bolt with its seat and cap constitutes the subject matter of the present invention, as will now be described.

The seat member 5 comprises a sleeve screwed into the outside sheet 1 of the fire box by an external thread 5, preferably tapered to insure a steam-tight lit; said sleeve having an enlarged upper end 5 formed with a concaved recess 5" to receive the head 3 of the bolt, and this enlargement being formed with a thread 5" preferably straight and on the outside, to receive the threaded cap (5. The cap thread is not required to be absolutely steam-tight, since the cap is C(HlSiZlllCtQtl with a sealing shoulder 6 pressing tightly and grinding upon the upper edge of the sleeve 5, as the cap is screwed home, which makes a tight joint at that point. lvloreovcr, the bolt head is fitted to its seat with sullicient accuracy to prevent escape of steam when the boiler is under pressure and the bolt subject to tension.

The head of the bolt and the concave seat formed in the sleeve provide a ballandsocket joint, which allows limited angular movement to the bolt in any direction without diminishing the bearing of the head in the seat, so that the bolt can accommodate or adjust itself automatically in harmony with any movement or vibration which may develop in the lire box in consequence of changes in temperature or shocks transmitted from the track.

The enlargement of the upper end of the sleeve permits the concave bearing to be made larger and to be located immediately over the straight wall 5 of the sleeve, without making the wall of the sleeve unduly thick or tapering it. Moreover, it accommodates a laterally enlarged head with corresponding increase in the radius R of the surface with which the head bears upon the seat, thereby greatly increasing the angle of this bearing surface to the axis of the bolt and correspondingly reducing the wcdging effect and consequent tendency to split the sleeve when excessive loads are imposed upon the stay bolt. A further advantage of the lateral enlargement of the sleeve and the location of the concave seat vertically above the relatively thin cylindrical body of the sleeve, accrues from the increased clearance between the neck of the bolt and the inner surface of the sleeve extending from the head to the lower end of the sleeve, and the avoidance of taper or reduction in the upper end of this space with consequent liability to retain and accumulate scale and sediment, which in some forms of stay bolt construction, eventually pack around the bolt suiiiciently to prevent its yielding.

The upper portion of the head of the bolt is constructed on two different curves, to wit, a side curve, the radius r of which is less than half the greatest cross dimension of the head, and a top curve, the radius r of which is approximately equal to said dimension, with the result that surplus metal and unnecessary weight are wholly eliminated without removing metal necessary to afiord shearing resistance. This construction permits the use of a relatively low cap without sacrificing any of the advantages of the cap space.

The general shape of the bolt head resulting from the characteristics of construction above described is elliptical in axial section which, while aifording the necessary wide ball bearing seat with increased angle of bearing surface, permits the embodiment of a minimum weight of material with a maximum strength and durability. It also adapts the bolt to be made by pressing or upsetting with ease; and hence tends to cheapness in construction as well as in material. These same considerations also enter into the construction of the sleeve providing the seat and the cap appropriate. to the particular construction of sleeve and bolt head.

In forming the head, its lower bearing surfaces will be constructed upon an arc struck from a center which is considerably beyond the greatest cross dimension of the head and preferably with a radius that is greater than half the diameter of the head so as to give the increased angle to the radius to reduce the tendency to split the sleeve by wedging action. The sides of the head above the bearing surfaces will be'constructed upon two radii considerably less than the diameter of the head, while the outer surface will be constructed relatively flat by selecting an arc whose center is well beyond the greatest cross dimension of the head. The head is joined to the neck of the bolt by fillets to avoid a sharp angle and the center of the outer surface of the head may be provided with a faced recess to receive a tool for screwing the bolt into the inner sheet.

A further advantage arising from this construct-ion is that bolts of different diameters can be used with the same seating attachment, so that when a broken bolt is removed from the inner sheet, necessitating reaming and rethreading of the opening, a larger bolt fitting the new opening can be introduced into the same seating attachment.

I claim A self-adjusting stay bolt for uniting two members, comprising a body portion adapted to connect with one member, anda head adapted to cooperate to efiect a ball and socket bearing upon the other member, said head being formed with an inner spherical bearing face constructed upon an arc whose radius is greater than half the greatest cross dimension of the head, whereby the wedging action of the head is reduced; said head also having its crown constructed on two different curves, to wit, a side curve, the radius of which is less than half said dimension and a top curve, the radius of which is approximately equal to said dimension.

The foregoing specification signed at Louisville, Ky, this 16th day' of October, 1912.

MILLARD F. COX.-

In presence of- E. B. VAUGHAN, H. R. CRULL.

copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. G. 

